1. Field of the Invention
The present invention relates to an imaging apparatus, an X-ray detector, and an imaging method.
2. Description of the Related Art
In the field of digital radiation imaging apparatuses, an equal-magnification optical system large-area flat panel type sensor using a photoelectric conversion element, instead of using an image intensifier, is widely used to improve the resolution, reduce the size, or suppress distortions of an image.
As discussed in Japanese Patent Application Laid-Open No. 2002-344809, it is conventionally proposed to realize a sufficiently large area of a flat panel type sensor by tiling a plurality of rectangular semiconductor substrates, which can be cut away from a silicon semiconductor wafer. A plurality of complementary metal oxide semiconductor (CMOS)-type image sensors is formed as photoelectric conversion elements on the obtained rectangular semiconductor substrate. The CMOS-type image sensor can realize high-speed reading, when the micromachining technique is employed, compared to an amorphous silicon type sensor. Further, the CMOS-type image sensor has high sensitivity. It is easy for the CMOS-type image sensor to obtain a large area compared to a case where a charge coupled device (CCD)-type image sensor is used.
Further, as discussed in Japanese Patent Application Laid-Open No. 2006-319529, it is conventionally known that an imaging apparatus can be configured to have a pixel addition function to perform binning processing for adding signals from a plurality of neighboring pixels, as a signal of one pixel. When reduction processing is performed based on the binning processing, an image having been subjected to the reduction processing may deteriorate due to the presence of a defective pixel. To solve this problem, it is useful to perform the processing without including any pixel signal of the defective pixel.
Further, a signal read from an image sensor includes random noises, such as thermal noises of an amplifier that reads the signal from the image sensor and disturbance noises of electronic devices. As a method capable of reducing the above-described random noises, it is conventionally known to read a signal stored during a single exposure operation plural times using an image sensor that has the capability of realizing a non-destructive signal reading operation and obtaining an average of the readout signals to reduce randomly generating noises.
It may be possible to perform the binning processing considering the presence of defective pixels together with addition processing of signals obtained in a plurality of non-destructive reading operations. In this case, if averaging processing of respective pixels is performed after completion of the binning processing considering the presence of defective pixels, it is required to perform the binning processing as much as frames having been non-destructively read out. For example, in a case where defective pixel positional information to be referred to in the binning processing is read out from an external memory in parallel with the binning processing, the processing speed tends to decrease because of an increase in the number of times the memory is accessed in addition to the number of times the binning processing is performed.